JPH0329116A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To stably produce an oriented coating film with good orientation by running a substrate coated with the magnetic coating material through a space between at least one pair of magnets disposed to face each other along the traveling direction of the substrate. CONSTITUTION:The substrate 1 coated with the magnetic coating material 2 is run through a space between at least one pair of magnets 3, 3' facing each other with magnetic poles along the traveling direction of the substrate. While the magnetic coating material 2 for the magnetic recording layer is applied on the substrate, high shearing stress is given to the coating material to cause some orientation of plate-type magnetic particles in the coating material. These particles which are priorly oriented to certain degree are further oriented by running the substrate through the space between the magnets, so that the axis of easy magnetization (in the thickness direction of the particle) of the magnetic particle is made parallel to the substrate surface by the stable magnetic field generated by the magnets parallel to the substrate. Thereby, the obtd. recording layer has good intrasurface longitudinal orientation. By this method, magnetic coating film containing oriented particles can be obtained without causing large disturbance of orientation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing a magnetic recording medium, and more particularly to a method of manufacturing a recording medium by applying a paint containing magnetic fine particles onto a substrate. ．． Conventional magnetic recording generally uses magnetization in the plane of a recording medium. However, with this recording method that uses magnetization in the in-plane direction, when attempting to achieve high recording density, the demagnetizing field within the recording medium increases, making it difficult to achieve a high recording density above a certain level. In order to overcome such limitations in recording density, a perpendicular magnetic recording method that uses magnetization in a direction perpendicular to the surface of a recording medium has been proposed in recent years. This perpendicular magnetic recording system has a characteristic that the demagnetizing field in the recording medium is reduced at high recording densities, and can be said to be a recording system that is essentially suitable for high-density recording.

Recording media used in perpendicular magnetic recording systems include continuous films such as CO-Cr vapor deposited films and coated films in which hexagonal plate-shaped barium ferrite fine particles are dispersed in resin. In particular, recently, from the cost advantage of coating type and practicality such as durability,
Coated film type perpendicular magnetic recording media are attracting attention.

In the case of a coated film type perpendicular magnetic recording medium, the grains used have an axis of easy magnetization perpendicular to the plate surface, and the axis of easy magnetization tends to be oriented perpendicular to the substrate surface during coating. However, even though magnetic powder is easily oriented,
It is not possible to obtain sufficient orientation by ordinary coating, and it is difficult to obtain a perfect perpendicular recording medium. on the other hand,
Barium ferrite m-type powder has a plate-like shape, is ultrafine particles, and has a plate thickness of 100 to 1000 angstroms, so it has potential as a longitudinal orientation medium.

As methods to increase this degree of orientation, methods have been implemented or proposed, such as a method in which the paint is oriented in a magnetic field of a constant strength after coating, or a method in which the viscosity of the paint is adjusted and the shear stress applied during coating is used to orient the paint. There is.

Problems to be Solved by the Invention However, when using the above-mentioned method, even if the viscosity of the paint is increased, sufficient dispersion cannot be achieved by shear stress alone during coating, and the viscosity of the paint is extremely high. It is difficult to obtain recording density. In addition, when aligning in a magnetic field using the conventional method, it is difficult to maintain the coating in a uniform magnetic field until it is dried and solidified after coating at high speed. In this case, the orientation is disturbed, which causes many unstable factors such as a decrease in the degree of orientation and the generation of noise.

As described above, the reality is that with conventional methods, it has been difficult to achieve both high distribution efficiency and stable productivity at a high level.

In view of the above problems, the present invention provides a well-oriented oriented coating film,
This provides a method for stable production.

Means for Solving the Problems In order to solve the above problems, the method for manufacturing a magnetic recording medium of the present invention includes a method of manufacturing a magnetic recording medium by attaching a substrate coated with a magnetic paint to at least one or more opposing magnets having magnetic poles arranged in the same direction as the substrate running direction. It is designed to allow it to pass through the gap.

Effect of the present invention The magnetic paint for shaping the magnetic recording layer is applied under high shear stress by passing a substrate coated with magnetic paint through the gap between the oriented magnets having the above structure, and the shear stress is reduced. The direction of the axis of easy magnetization (thickness direction of the plate-like particles) of the plate-shaped magnetic fine particles in the paint, which are oriented to some extent with respect to the substrate surface, is parallel to the substrate surface by the magnetic field generated by the stable magnet, which is parallel to the substrate surface. This results in a magnetic recording layer with very good in-plane longitudinal orientation.

EXAMPLE An example of the method for manufacturing a magnetic recording medium of the present invention will be described below.

Example 1 The following ingredients were prepared as a paint composition, put into a grind mill, and mixed and dispersed to produce a magnetic paint. ○Barium ferrite/Co-Ti substituted powder (average particle size, plate diameter: 0.01 μm, plate ratio (plate diameter/plate thickness)
:5, holding power 7500e)...100 parts ○Vinyl chloride polymer...11 parts ○Polyurethane...
...After applying the above magnetic paint onto the 11-part film-like substrate surface using a blade coater with a 35 μm blade and a 31-layer blade with a spacing between the blade and the substrate surface at a coating speed of about 1Qm/win. The coating film of Example 1 was obtained by passing through a gap between opposing magnets having magnetic flux in the same direction as the traveling substrate and drying and curing. FIG. 1 shows a cross-sectional view of the arrangement of the opposing magnets. 1 is a substrate, 2 is a magnetic paint, and 3 and 3' are orientation magnets. Example 2 The magnetic powder blended into the magnetic paint in Example 1 was replaced with barium ferrite/Co-Ti substituted powder (average particle size, plate diameter 0.05μ steel, plate ratio (plate diameter/plate thickness) 3, Coercive force 75
00e)-"...100 parts, and in the same manner as in Example 1 except that a coating film of Example 2 was obtained.

Comparative Example 1 A substrate on which a magnetic film was formed under the same conditions as in Example 1 was passed through a gap between oriented magnets with the same magnetic poles facing each other, and a sample was prepared in the same manner as in Example 1. I got it. FIG. 2 shows a cross-sectional view of the oriented magnet with the same magnetic poles facing each other. 1 is a substrate, 2 is a magnetic paint, and 4.4' is an orientation magnet. Comparative Example 2 A sample was prepared by applying the same coating material as in Example 1 on a 15 μm thick polyester film under the same coating conditions as in Example 1 without passing it through an orientation magnet, to obtain the coating film of Comparative Example 2. Ta. Comparative Example 3 A sample was prepared in the same manner as Comparative Example 1 using the same paint as in Example 2, and a coating film of Comparative Example 3 was obtained.

Comparative Example 4 A sample was prepared by applying the same paint as in Example 2 on a 15μ-thick polyester film under the same coating conditions as in Example 2 without passing it through an orientation magnet, and the coating film of Comparative Example 4 was obtained. Ta. In order to investigate the particle orientation state of the obtained coating film, the coating film was individually peeled off from the substrate and measured using a sample vibrating magnetization measuring device, and the squareness ratio in the in-plane direction (Mr/Ms) and the in-plane The orientation state was evaluated from the orientation ratio (Mr/Mr) in the direction and the perpendicular direction.

The squareness ratio and orientation ratio of these samples were as shown in Table 1.

In Table 1, Example 1, Comparative Example 1, and Comparative Example 2 are coating films made with the same paint using magnetic powder with a plate ratio of 5, and it is clear from the comparison of these three samples that the present invention Examples have a high degree of orientation.

In addition, Example 2, Comparative Example 3, and Comparative Example 4 are coating films made with the same paint using magnetic powder with a plate ratio of 3.
Comparing the samples, it is clear that the degree of orientation is higher in the example according to the present invention.As can be seen from the results in Table 1 below, the example using the present invention is higher than the comparative example without using it. The orientation ratio in the direction horizontal to the substrate surface and the squareness ratio are both larger than that of the sample, indicating that the method for producing a magnetic recording medium of the present invention is capable of obtaining a coating film with good orientation. It turns out that it is effective.

Here, a barium ferrite magnetic body with a plate ratio of 3.5 was used, but the present invention is not limited to this in any way.

In addition, a sufficient effect can be obtained if there is at least one opposing magnet whose magnetic pole is arranged in the same direction as the substrate running direction, but this is not limited to this in any way.

Effects of the Invention As described above, according to the present invention, a magnetic coating film with oriented particles can be obtained without major orientation disturbance after applying the magnetic coating material. Therefore, it is possible to provide a very useful manufacturing method as a method for obtaining a recording medium with high distribution properties that rival high-density recording.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of an orientation magnet according to an embodiment of the present invention, and FIG. 2 is a side sectional view of a conventional orientation magnet. l...Base, 2...Magnetic paint, 3.3
'4.4'...Orienting magnet.

Claims (1)

[Claims] A magnetic paint in which magnetic fine particles having a plate-like shape and an axis of easy magnetization are dispersed in a direction perpendicular to the plate surface is applied to the gas, and the magnetic fine particles are oriented in a horizontal direction on the coating surface. A method for manufacturing a magnetic recording medium having an axis of easy magnetization, characterized in that a substrate coated with a magnetic paint is passed through a gap in which at least one opposing magnet having magnetic poles arranged in the same direction as the traveling direction of the substrate is disposed. A method for manufacturing a magnetic recording medium.